It's a historic day on the campus of Northwestern University. Football players there became the first college athletes in this country to vote on whether to unionize. The results may not be known for some time. The National Labor Relations Board is reviewing Northwestern's appeal of an earlier ruling to allow this union vote to take place. NPR's David Schaper reports.

DAVID SCHAPER, BYLINE: The atmosphere here on the Northwestern campus is a bit tense as there's a lot riding on this vote by scholarship football players on whether or not to be the first in the country to join a college athletes' union. I'm standing outside of Ryan Field, Northwestern's football stadium, where players cast their ballots either before or after a mandatory offseason team training session this morning. None would talk about how they voted but one did tell NPR how he feels now that the voting is over.

TRAVEON HENRY: It's relieving to get it done with.

SCHAPER: I caught up with sophomore starting safety Traveon Henry as he and a teammate were walking to their car to go off to class.

HENRY: It's another plate off of our table, so get back to football.

MICHAEL ODOM: It's a big mess, you know.

SCHAPER: Sophomore Michael Odom was a reserve linebacker for the Northwestern Wildcats.

ODOM: There's a divide amongst the players. There are the guys who are supportive of the union, and there are the guys who obviously are against the union.

SCHAPER: Odom says he's still close to some of his former teammates even though he just quit the football team this winter.

ODOM: I left the team because it was overwhelming. As someone who's - who has big career aspirations outside of football, trying to balance those with football was very difficult. And it's very difficult for a lot of guys.

SCHAPER: Odom was a walk-on player, meaning he wasn't getting a scholarship to pay his tuition. And he says that actually gave him the freedom to walk away from football when the demands of the program started to bring down his grades. He says many of his teammates don't have that option because they couldn't afford to be at Northwestern without the football scholarship.

ODOM: You know, that puts a lot of pressure on them to perform football before school, the way I see it.

SCHAPER: Odom says the scholarship and the amount of control that the football program has over players' daily lives also makes it difficult for players to not succumb to what he says was heavy-handed pressure from coaches and university officials to vote against joining the union. Some players, their families, alumni and organizers of the College Athletes Players Association, the union the players were voting on whether to join, alleged that Northwestern crossed the line in trying to influence players' votes.

ALAN CUBBAGE: That is simply not true.

SCHAPER: University spokesman Alan Cubbage told reporters after the voting was complete that Northwestern officials conducted their campaign in accordance with NLRB rules that are laid out under federal law.

CUBBAGE: In doing so, we did indeed explain very consistently and very clearly the university's position, which is that we believe our students are students, not employees, and that we don't believe unionization and collective bargaining are the appropriate method.

SCHAPER: The Chicago regional director of the NLRB ruled in March that the football players are university employees who often work at their sport 50 to 60 hours a week and, therefore, they can vote on whether to join a union. But the full National Labor Relations Board in Washington has agreed to review that ruling and hear Northwestern's appeal, a process that could take months. In the meantime, the NLRB has impounded the ballots. And it may be sometime before the results of today's union election are revealed. David Schaper, NPR News, Chicago. Transcript provided by NPR, Copyright NPR.